RE: [xwiki-users] Date value compare (and update on date arithmetic)

Jérémi: You make it look easy, but it took me a good long bit of searching and trial-and-error investigation to figure out how to get a real Date object out of an XWiki object field. And you perform a little leger-de-main which I have not found explained anywhere: the expression $obj.XWikiObject.date.value is equivalent to $obj.XWikiObject.getDateValue("date"). Unfortunately, this is not suitable for use as an lvalue, but it makes a nice shorthand. Is this documented anywhere (other than in the source)? I noted the same thing when I found, in some sample code, a call to a (seemingly) nonexistent method $xwiki.getCalendar(). Happily, simply writing $xwiki.calendar in a document yielded an object identifier containing the classname com.xpn.xwiki.plugin.calendar.CalendarAPI, so it seems that XWiki was fiddling my call into $xwiki.get("calendar"), which is documented to return a plugin API, which before this had meant nothing to me (either that, or the plugin augmented com.xpn.xwiki.api.XWiki with a getCalendar() method, which is what I thought before I saw the above). Velocity, of course, turns any rvalue reference to $obj.foo into a call to $obj.getFoo() or $obj.getfoo(), and likewise any lvalue reference in a #set into a call to $obj.set[Ff]oo() with the RHS as its argument. But this trick is different, because at least in the first case it has to know the navigation of a particular XWiki-specific class hierarchy. Nice shorthand; would be nicer if it were explained somewhere... Okay, I'll do it... By the way, that $xwiki.calendar property finally got me to an answer to my date arithmetic problem, thanks to Java reflection. The task was in a project status reporting page, where I wanted to ignore records more than a week old. The problem was that I could find no way at all to do date arithmetic in a Velocity script, because the time value returned from java.util.Date.getTime() is a long integer, which (until the next release of Velocity, at least) can't be used in an arithmetic expression. I could have used the Date functions to format a date, manipulate the string version, and then parse it, but that would be far too difficult, inflexible, and error-prone even ignoring the fact that those methods were deprecated. It works like this, for those who are interested: First, $xwiki.calendar has a method getCalendar() which, in the version without arguments, returns a java.util.Calendar initialized with the current date. Because it inherits from java.lang.Object, it is Cloneable, so I clone()d it to get a copy that I could set back seven days, without disturbing the original object (I learned this the hard way: the returned object was a reference, and changes via the copied reference changed the original). Turning back the clock in a java.util.Calendar by seven days is quite simple in Java - formally speaking, it's java.util.Calendar.add(java.util.Calendar.DAY_OF_YEAR, -7). However, this isn't Java exactly; we can call the add() method easily enough, because we have a Calendar object, but that DAY_OF_YEAR symbolic constant isn't accessible that way, because apparently Velocity doesn't translate field references, only method calls. The final expression was $xwiki.calendar.calendar.class.getField("DAY_OF_YEAR").int #set($wcal = $xwiki.calendar.calendar.clone()) ## copy of java.util.Calendar with current time $wcal.add($wcal.class.getField("DAY_OF_YEAR").int, -7) ## set the calendar back one week. #set($weekago = $wcal.time) ## get the resulting date as a java.util.Date object After this, when I wanted to see whether date "donedate" from an object was more than a week old, I wrote something like this: #set($weekold = $obj.xWikiObject.donedate.value.before($weekago)) which worked just fine. Of course, since I also wanted to sort those records on other than the default field, I needed to do an $xwiki.search() call with a custom query, and SQL can easily do date arithmetic. That brings up another topic, because I was foolish enough to try it... brain[sic] -----Original Message----- From: jeremi joslin [mailto:jeremi23@gmail.com] Sent: Wednesday, March 22, 2006 8:25 AM To: xwiki-users(a)objectweb.org Subject: Re: [xwiki-users] Date value compare On 3/22/06, jjanssen(a)nl.swets.com <jjanssen(a)nl.swets.com> wrote: I do it a while ago using the before function: #if ($obj.XWikiObject.date.value.before($xwiki.getCurrentDate())) Jérémi -- Blog: http://www.jeremi.info LinkedIn: https://www.linkedin.com/profile?viewProfile=&key=1437724 Project Manager XWiki: http://www.xwiki.org skype: jeremi23 -- msn et gtalk : jeremi23(a)gmail.com